Lifespan: Eishō 10 (1513) to 1/16 of Eiroku 8 (1565) (under another theory he was born in Meiō 4 (1495))
Rank: shugo daimyō; lord of Okishio Castle
Title: Junior Fifth Rank (Lower), Master of the Eastern Capital Office
Bakufu: Muromachi bakufu – Military Governor of Harima, Bizen, and Mimasaka provinces
Lord: Ashikaga Yoshiharu
Father: Akamatsu Yoshimura
Siblings: Harumasa, Masamoto
Children: Yoshisuke, Noriie, daughter (wife of Akamatsu Masahide), daughter (wife of Miki Michiaki)
Akamatsu Harumasa served as the eleventh head of the Akamatsu clan and as the shugo daimyō of Harima, Bizen, and Mimasaka. He was lord of Okishio Castle in Harima. Harumasa earned the Court titles of Junior Fifth Rank (Lower), and Master of the Eastern Capital Office. The title of Junior Fifth Rank (Lower) was often conferred upon those persons who provided donations to support the construction and operation of facilities for the Imperial Court and temples and shrines under their dominion. With Kyōto being the location of the central authorities, the Master of the Eastern Capital Office (the highest of the four official positions of the ritsuryō system of governance) was appointed to govern the east of Kyōto (to the left of the south-facing throne).
In 1520, Harumasa’s father, Akamatsu Yoshimura, lost in a power-struggle against Uragami Muramune, the deputy military governor, of Bizen Province. As Yoshimura was forced into retirement, Harumasa succeeded him at the age of eight. In the autumn of 1521, Yoshimura was assassinated following a second confrontation with Muramune. Harumasa temporarily joined with Muramune to oppose an invasion by the Yamana, but after this threat subsided, the Akamatsu and Uragami clans fought again, causing Harumasa to be driven from his base at Okishio Castle and flee to Shinjōyama Castle in Mimasaka Province.
In 1531, Muramune invaded Settsu Province in support of Hosokawa Takakuni, a kanrei, or deputy shōgun. Takakuni battled against Hosokawa Harumoto for control of the Muromachi bakufu in Kyōto. Although Harumasa served as the rear guard for Muramune, he had committed to betraying the Uragami by secretly sending hostages to Ashikaga Yoshitsuna, the Sakai kubō, or shōgun of Sakai. This role represented a form of leadership in absentia during a period of internal conflict among and between the Ashikaga and Hosokawa clans for control of the Muromachi bakufu in Kyōto. While camped at Kannō Temple, Harumasa colluded with Harumoto to plan a pincer attack on Takakuni and Muramune in a conflict known as the Collapse at Daimotsu (Daimotsu kuzure). Harumasa attacked from the rear, Harumoto’s men attacked from the flanks, while Miyoshi Motonaga led forces from the front, decimating the army under the command of Takakuni and Muramune. Muramune was killed in the battle while Takakuni was apprehended after attempting to hide in a dye shop in the neighboring town of Amagasaki and ordered to take his own life several days later.
This action enabled Harumasa to restore some of his influence, but the conflict persisted with Muramune’s sons, Uragami Masamune and Uragami Munekage. In 1534, a battle unfolded on Mount Asahi in Himeji. In 1537, an invasion by Amago Akihisa of Izumo Province led to chaos in Harumasa’s territory despite obedience by the Uragami. Meanwhile, Uno Murayori, a retainer from Shisō, betrayed Harumasa. In 1538, while calling upon the Kajiwara clan at Takasago Castle for support, Harumasa incurred an attack by Kodera Norimoto and Akashi Masakaze, who also betrayed him. Harumasa then fled for protection to Tamura Noto-no-kami in the village of Gunge in Awaji Province. In 1539, Harumasa, with support from the Hosokawa of Awa Province, landed in Akashi and attacked Edayoshi Castle. However, upon hearing a rumor that the Bessho clan at Miki Castle (who had resisted the Amago until the end) were intending to betray the Akamatsu, Harumasa safely fled to the Kaiei Temple in Sakai.
During the period from 1540 to 1541, a failed expedition by the Amago into Aki Province that ended in the Battle of Yoshida-Kōriyama caused them to retreat from Harima. While Harumasa avoided a crisis in his territory, the Akamatsu clan continued to suffer a loss of authority. It was during this period that Harumasa received one of the characters from Ashikaga Yoshiharu, the shōgun, for his own name.
In 1552, the appointment of Amago Haruhisa as the military governor of Bizen and Mimasaka meant that Harumasa lost these two provinces from his domain. Meanwhile, the Uragami continued to encroach on his domain in Harima. In 1558, Kodera Masamoto backed Harumasa’s eldest son, Yoshisuke, in a coup d’ètat, causing Harumasa to flee to Tatsuno Castle occupied by Akamatsu Masahide, his son-in-law. These events led to the disintegration of the Akamatsu clan and sōryō, or lineal inheritance. The leaders of the clan lost the territorial authority conferred upon them as shugo daimyō and members of the landholding class. Harumasa moved the remnants of his power base to northern Harima and Mimasaka, and managed the domain together with the Mōri and local landholders including the Sagayama, the Hiroto, and the Toyofuku, until his demise in 1565.